1. Field of the Invention
The invention relates to collapsible, reusable enclosures, in particular to general purpose shipping boxes formed of extruded polymeric materials.
2. Description of Related Art
For better understanding of the present invention, it would be expedient to review the general purpose shipping box industry.
Businesses, both nationally and internationally, require an increasing number of boxes in which to store and ship goods. Currently, the box market is dominated by basically standardized general purpose shipping boxes made from corrugated paperboard. The appearance of many standardized boxes is often customized in terms of color and lettering.
In order to grasp the size of the shipping box market, in 1994, according to Fiber Box Association""s 1994 Annual Report, US paperboard mills shipped 28 million tons of boxboard (see pg. 1 of the aforementioned Annual Report of the Fiber Box Association), worth over $18.5 billion dollars (see pg. 3), most of it for domestic use. (Boxboard is defined as xe2x80x9cpaperboard components from which . . . paperboard [is] manufacturedxe2x80x9d, see pg. 16 in the Annual Report). In 1994, 77.3% of the shipping boxes made of the aforementioned boxboard were used for shipping non-durable goods (see pg. 6 in the Annual Report). According to our market research, in the US alone 20 to 40 billion corrugated paperboard boxes are made annually and after only one use discarded.
The term shipping box means a rigid, rectangular container which is used for shipping and often also for storing various products; a shipping box may be with or without a lid. However, when referring to the boxes described in various sources, e.g., patent specifications, we at least once apply the terms by which they are called in the source material, such as containers, crates or cartons. The term general purpose shipping box does not have a well-established definition. It is understood that it should be of a standard dimension and/or capacity prescribed by Federal law or other competent authority; the freight shipping requirements of such boxes are specified in Rule 41 of the Uniform Classification of the National Motor Freight Classification. In this writing, the term general purpose shipping box is used to indicate that the design of such box is not product-specific in: its shape; the way it is assembled from its layout(s) before loading; the way it has to be loaded; and the way it has to be disassembled after it is emptied. Design of a general purpose shipping box should be suitable for loading it in a free-standing position with loose or granular material of reasonable size particles, such as apples, loose candy, or nuts and bolts, or bags of fine-particle substances, or wrapped or not wrapped items of consumer goods.
These boxes are shipped to customers as unfolded, often partially assembled flat layouts, and assembled into three-dimensional boxes wherever the packaging takes place. The assembly is performed by folding pre-creased layouts so that a flap attached to one panel folds over the flaps of another panel, and then locking the foldups into their places.
Smaller packagers usually use foldable corrugated paperboard boxes that have special locking elements, usually in the form of notched tabs, which mate with corresponding slots cut through the layout of the box. Larger-scale packing operations assemble their crates on special assembling (erection) machines which erect and then fasten boxes by more permanent means, such as by glue or staples.
There are some plastic boxes on the market, both collapsible and of permanent shape, but all the plastic boxes, sometimes called containers, are aimed at special niches. Because of their current high cost, boxes made from polymeric materials can compete with the corrugated paperboard shipping boxes only in these specialty markets where wet-strength, multiple use or some other specific requirement becomes an overwhelming issue.
In the context of the present invention the term collapsible is defined for all container-type enclosures as being constructed in such a manner that, when empty, such a three-dimensional enclosure can be collapsed or disassembled to about {fraction (1/10)} or less of its erected size.
The term corrugated refers to a packaging material consisting of a central member (medium) which has been fluted on a corrugator and to which one or two flat sheets of paperboard have been glued. The term xe2x80x9ccorrugatedxe2x80x9d is also used for polymer sheets which mimic loosely the design of corrugated paperboard. Corrugated polymer sheets will be discussed in the section on the current art of making polymer boxes from such sheets. The term paperboard is the term used by the packaging industry for paper which is thicker than 12 points (0.012xe2x80x3).
There are a number of inherent problems arising from the use of corrugated paperboard boxes. The actual strength and environmental resistance of paperboard is determined by the ties between its fibers. These ties are not molecular (chemical) type, as they are in polymers. The ties between fibers in paper, formed by drying a layout of colander-squeezed pulp, are weak even under the most favorable of circumstances. The ties deteriorate completely when the moisture content in this absorbent material rises above the saturation value. Rodents are known to make holes in paperboard boxes. For comparison, most of the polymers used in the packaging and appliance industries have much higher resistance to stress and environmental hazards, such as too much or too little moisture; unlike paperboard, these polymers can be submerged in water with little change in their performance.
In order to increase the resistance of paperboard boxes to moisture in these applications when the product itself is associated with moisture, e.g., lettuce, meat or even frozen fish, or when the boxes with the product will be submitted to the elements, e.g., in military applications, the paperboard for such boxes is previously waxed or treated with chemicals. That adds 50% or more to the price of such wet-strength paperboard boxes, and increase their weight.
There is another shortcoming of paperboard boxes: the porous structure of paperboard lowers its hygienic qualities, as bacteria or other contaminants can easily be absorbed. It is possible to restrict penetration of contaminants into paper by creating a barrier layout. However, this is not only quite expensive, but it also alters the recycling or disposal of such boxes.
Once these 28 million tons of paperboard boxes annually are used, they are discarded and destined either for a landfill or for recycling. In either case this presents US society with considerable environmental and recycling problems. Recycling of paper products is not a cheap or simple process. It involves going again through the making of pulp, which also involves neutralization of hazardous byproducts, mixing recycled pulp with fresh, and the making of paper. Only then can one produce a recycled corrugated sheet. Recycling of polymers used in consumer goods (with the exception of those polymers which were used in batteries or in some other hazardous application) is extremely simple by comparison: the three major steps of recycling plastics are: simple grinding, mixing the grinds with additional new components to replenish their quality; and getting the mix ready for new production via melting, e.g., in an extrusion.
Also, the process of making paperboard uses a great amount of toxic chemicals that need to be recaptured from the technological waste stream and neutralized. The environmental clean-up operations weight heavily on the overall cost of paperboard boxes.
An additional factor in the use of paperboard is the uncertainly surrounding the paper industry, especially regarding the availability of wood pulp to meet the fluctuating needs for paperboard. It takes many years and a large investment to build a papermill, and sometimes even longer to get permission to build one in a given area; but it takes only one decision of some pertinent governmental body to add restrictions on harvesting trees in some given area of timber growth. Because of the aforementioned uncertainty, in 1995 the U.S. price of pulp rose over 30%, from $600 to $900/ton. In 1996 some new papermills became operational, and the price of pulp went down again. The climate of uncertainty is further enhanced by frequent regulatory changes regarding recycling of paperboard, and regarding landfills.
While the use of plastic boxes eliminates some of the above cited inherent problems of the paperboard box industry, the current art of designing and manufacturing plastic shipping boxes is too expensive to compete with corrugated paperboard boxes anywhere but in specialty markets.
Currently used collapsible plastic enclosures, e.g., shipping boxes, fall into one of two broad groups. The first group consists of collapsible plastic enclosures which mimic the paperboard box industry with this difference: instead on cutting layouts out of a sheet of corrugated paperboard, the layouts are cut out of a plastic sheet. Thereafter the plastic layouts are creased, folded and fastened by traditional means of the paperboard box industry: flaps of the layouts are fastened to their respective places by gluing, stapling, or inserting special locking elements, usually in the form of notched tabs, into corresponding slots cut through the layouts. Apart from extrusion of plastic sheet instead of corrugating paperboard into corrugated sheet, these collapsible enclosures have not incorporated any of the opportunities offered by plastics as a vastly different material into their design and production technology.
Collapsible boxes for asparagus made of extruded hollow sheet of corrugated polyethylene and marketed by Advanced Box Corporation of Tracy, Calif., are a case in point. These boxes are assembled by inserting a number of tabs into corresponding slots, just as one assembles that kind of paperboard box. This process requires either costly manual labor to insert all of the tabs, or special machinery. It is also difficult to remove all of the tabs from the slots to collapse the boxes for future use.
Characteristically, there are a number of patents on various design solutions of this group which claim both xe2x80x9cpaperxe2x80x9d and xe2x80x9cvarious materialsxe2x80x9d, which includes polymers. Thus, U.S. Pat. No. 2,757,851, issued to George Moore, describes a container made of a plurality of generally elongated blanks of relatively rigid or semi-rigid material which are fastened into enclosures by gluing tabs to the mating surfaces.
Strictly speaking, boxes with either stapled or glued/welded flaps are not reusable as such: a layout of a disassembled enclosure which was stapled, glued or welded during its assembly is no longer the same as before its assembly. Still, designs of this group are preferred by the paperboard box producers who want to expand into making plastic boxes as an alternative to the wet-strength paperboard boxes. Therefore, this subdivision of xe2x80x98almost reusablexe2x80x99 plastic boxes has to be considered. Furthermore, any new truly reusable polymer shipping box, before it will establish itself in the marketplace well enough to support a servicing substructure necessary for recirculation (e.g., retrieval and cleansing of already used boxes), has to compete against the polymer boxes designed like corrugated paperboard boxes.
Corrugated plastic sheets used for the enclosures such as shipping boxes are between 2 and 5 mm thick, with 0.2 to 0.3 mm thick side-walls, and 0.1 to 0.25 mm thick ribs between them, spaced about one thickness of a sheet apart. They are usually made from high density polyethylene or polypropylene; other polymers are either too brittle, e.g., rigid PVC, or too expensive, such as PET.
Pound per pound, these thin-rib corrugated sheets made of high density polyethylene or polypropylene are more expensive and less rigid than the corresponding corrugated paperboard in its dry state. The lesser rigidity of the corresponding corrugated polymer sheets is due to two factors: the high shrinkage and the low rigidity of the polymers currently used for these thin-walled corrugated polymer sheets.
The high shrinkage leads to substantially bent spacing ribs in the thin-walled corrugated polymer sheets which reduces the rigidity of these sheets. The rigidity of these polymer sheets is further reduced by low modulus of elasticity of the polymers currently used for such sheets. Modulus of elasticity of high density polyethylene is around 930 MPa, and of polypropylene around 950 MPa. In comparison, the modulus of elasticity of wood in the direction of its growth, which affects the rigidity of paper, is from seven to fifteen times higher (7,000 to 14,000 MPa).
In other words, corrugated sheets made from pure high density polyethylene, polypropylene and a host of other pure polymers are not well suited for general purpose shipping boxes: either they are too brittle, or their price is at least twice as high as that of the stability-wise compatible corrugated paperboard under conditions favorable to paperboard environment. In other words, corrugated plastics sheets made of pure polymers are either too expensive to compete with paperboard for general purpose enclosures, or not enough rigid to withstand the same transportation stacking height as paperboard enclosures can in favorable conditions.
Another serious shortcoming of the enclosure designs of this group is that they repeat all the typical shortcomings of the corrugated paperboard box designs. For instance, only from 60% to 80% of the sheet goes to form the outside panels of the enclosure; the rest goes to multi-layered foldups and cut-offs.
Most of the collapsible plastic boxes the design of which depart from traditions of the corrugated paperboard industry are designed for production by molding. One of quite common features of such designs is that two functions, that of positioning and that of retention of the connection between panels of the same layout, or the adjacent panels of different layouts, are achieved by separate means.
Here is an example of such a design. A knockdown shipping container, described in U.S. Pat. No. 3,675,808, given to D. Brink in July 1972, presents a single foamed polystyrene layout which is erected into a five-panel enclosure by folding up two side walls (14 in FIG. 1 [when discussing the prior art here and hereinafter, the reference numerals belong to the descriptions and drawings of the corresponding patents under discussion]) along the special folding grooves (18 in FIGS. 5 and 7), and two end walls (12 in FIGS. 1, 2 and 3). The vertical joints between the adjective vertical panels (the respective side walls and end walls) are in position when the ears (26 in FIGS. 1 and 3) of the side walls 12 are thrust into the complimentary openings (28 in FIGS. 1 and 3) formed into the end walls 14. The retention of the vertical joints is attained by a strip of adhesive tape secured around the outer surfaces of the end and side walls. Such a connection is not reliable. Also, in order to disassemble such a shipping container, the adhesive tape has to be peeled off. In that sense, the connection between a pair of folded up adjacent side walls is irreversible: a new adhesive tape is required for the next assembly.
Here is another, more sophisticated version of the same kind of design solution, where the positioning and retention of a vertical joint of two adjective vertical panels are provided by separate means. In U.S. Pat. No. 3,924,798, given to S. Seveth in December 1975, the positioning is secured by a system of grooves and edges, whereas the retention of the assembly and disassembly of the box is provided by snapping closed and un-snapping four pairs of alike hooks (marked 168, 170, 176, 178, 180, 182, 172 and 174 in FIG. 6), where a hook is interlocked with its complementary hook when inserted into it under a 90xc2x0 angle. The retention capability of such interlocking hooks has to be overpowered in order to disassemble the enclosure; since a latching-type retention elements are not used in this design, either the retention ability of such directly elasticity-and friction-dependent interlocking elements is low, or the elements are bound to lose some of their former retention capacity after each assembly and disassembly.
U.S. Pat. No. 3,497,127, given to T. Box in February of 1970, the container is assembled and disassembled by locking and un-locking four complicated special interlocking elements or flaps (16 in FIG. 1) which have special retention slots in the mating walls. One of the shortcomings of this design is that the walls (12 in FIG. 1) of the filled plastic case are retained strongly in one direction, much less strongly in the opposite direction.
In U.S. Pat. 4,235,346, given to J. Ligget in November 1980, the vertical positions of the assembled side walls (13, 14, 14a and 15 in FIG. 1) are guided by four edges (20xe2x80x2 in FIG. 1) and the respective grooves (25 in FIG. 1). But the retention germane to the functioning of the container is secured only after the lid (17 in FIG. 1) is closed.
In U.S. Pat. 5,501,354, given to P. S. Stromberg in March of 1996, the grooves (marked C in FIG. 1) in the end panels (16 and 16A in FIG. 1) and the complimentary edge along the vertical edges of the side panels (14 and 14A in FIG. 1) define the positions of the vertical edges of an assembled collapsible container, but the grooves and edges by themselves do not provide for the appropriate retention for the working of the container. The retention is performed by four separate hinged locking flaps (marked f in FIG. 1).
In U.S. Pat. 5,551,568, given to Niles et al. in September 1996, the positioning of the respective side walls is secured by tongue and groove connections, whereas the retention is secured by interlocking two separately placed latches (52 in FIGS. 1, 2, etc.) of both layouts with the respective special seats formed in the opposite layouts.
All the aforementioned designs of this group are geared for molding. Molding of polymers, however, is not cheap. Molding as a manufacturing technology, especially injection molding, has three major shortcomings. First, the molds have to heated and cooled once every production cycle, which is wasteful of energy on two accounts: the energy is pumped into usually massive metal molds, and thereafter the molds are artificially cooled down for the next cycle, the same energy being pumped into the cooling system with little recovery. Only a small portion of the total energy used goes for forming the product from resin.
Second, the material should be cooled down considerably while still in the mold, which is time-consuming for labor and equipment alike. Third, the, valves, cylinders, clamps, and other attributes of the molding machinery are in constant change, which requires a sophisticated system of controls, as well as highly skilled set-up people. Besides, injection molding is associated with runners which need to be removed, reground and reused.
The need for centralized cooling demands that injection machines should operate in clusters of usually eight molding machines. In other words, there is no such thing as a small but efficient injection molding operation with two-three small machines.
Production via polymer extrusion, on the other hand, is the most effective method of production. In addition to being continuous in its mode of operation, it is free of all the above-mentioned shortcomings of molding. Unfortunately, there are very few designs of polymer enclosures specially geared for extrusion which do not mimic designs of boxes made from paperboard.
Clarey, et al., in U.S. Pat. No. 5,066,832, Plastic Enclosure Box for Electrical Apparatus, issued in November 1991, discloses an extruded plastic box formed of multiple, differently-shaped sections adapted to receive metal and plastic inserts. This box is not designed for disassembly, and is difficult and expensive to fabricate.
An interesting solution for a particular feeding problem is provided by Boeckmann, et al., in their Carrier Tape, U.S. Pat. No. 4,708,245, given in November 1987. This invention provides a solution for storage, transportation and automatic feeding of small and/or measured items, such as electronic components, pharmaceuticals and similar products. The carrier tape is formed of extruded plastic, and has interlocking joints extruded into the profiles of its stripe-like elements. The interlocking joints have retention elements built into them. Sprockets are provided for driving the tape. The components of the carrier tape are significantly different in shape, and thus have different manufacturing requirements. Further, the base-and-cover-strip construction of the carrier tape cannot be collapsed to minimize storage space. However, the carrier tape of the aforementioned invention cannot be redesigned into a five-sided enclosure.
Here is another invention allowing the use of extrusion of a continuous web with interlocking profiles for making enclosures. In U.S. Pat. No. 4,299,070, given to Oltmanns, et al., in November 1981, and titled Box Formed Building Panel of Extruded Plastic, a four-sided enclosure is discussed. A building panel is formed of multiple extruded plastic components joined together by a wedge-shaped projection fitting into a sealant-containing groove. This invention has a number of shortcomings: First, it provides only for four-sided enclosures. Second, the multiple components of this panel must be separately fabricated, and precisely inserted. Third, the enclosure cannot be easily disassembled.
In the late 1980-es, the Italian company CRandS in Roletto, using the expertise of another Italian company (the KARTO in Bressanno) in extruding wood-filled polypropylene sheets for the automotive industry, adjusted that technology for mass production of so-called fruit crates. CRandS""s fruit crate is a lidless, collapsible container which holds about 18 1b. to 20 1b. of product. It is meant for field-gathering of table grapes and other fruits, and their direct delivery to the marketplace.
One unique feature of this fruit crate is that the sheet for the crates is made from only 10% to 20% of virgin polypropylene resins; the rest is reground polypropylene (30% to 40%), and wood chips (about 50%).
Their collapsible, reusable fruit crate is made of a combination of extruded sheet material and molded corner pieces. The four corner pieces per crate added the high cost of injection molding from new resin. No wonder the cost of their four molded small corner pieces is over 30% of the overall cost of a fruit crate.
In order to improve the rigidity of their fruit crate, special rigidity ribs are vacuum-molded in all four sides and the bottom of their open-top enclosure. That added the cost of four plastic sheet forming machines and molds to the overall equipment, increased the cost of labor, and more than doubled the cost of energy.
The special rigidity ribs, together with some other design aspects, added $500,000 in special tooling cost for each particular size of product, to say nothing about the time and expense of setting up different tooling at every change-over.
Their design is associated with stamping out about 37% of the sheet material. And, because of their wood-filled composition, they have difficulty reusing it.
All collapsible plastic boxes known to us, including the aforediscussed CRandS""s fruit crates, are not versatile enough in their applications or technologically sound enough in their production options to offer a viable substitution for the currently dominant general purpose shipping box made from corrugated paperboard.
It is an object of this invention to provide a collapsible, three-dimensional enclosure with at least five side surfaces made from extruded inexpensive plastic material which is reusable, simple and versatile in design, advantageous in the use of the direction of extrusion for maximum strength of the enclosure, easy to assemble without using glue, staples, adhesive tapes, additional corner pieces, overlapping retention flaps or other added means of retention, easy to disassemble without the need to overpower the retention capacity of interlocking elements, easy and inexpensive to manufacture, suitable for an in-line mass production, may be produced practically without any production wastes, and is superior to the currently used corrugated paperboard shipping boxes.
These and other objects and advantages of the present invention will be more apparent from the ensuing description of the invention with reference to the accompanying drawings.
The invention provides a collapsible three-dimensional enclosure having at least five side members and comprising at least one first layout that contains at least one of the side members and at least one second layout that contains at least two of the aforementioned side members interconnected through a foldable connection. The first layout and the second layout each has a substantially rectangular configuration defined by a first pair of parallel edges and a second pair of parallel edges which are substantially perpendicular to the first pair of parallel edges. Locking elements are formed in the proximity to at least one pair of the parallel edges of the second pair of parallel edges. These locking elements are selected from the group consisting of a male locking element and a complementary female locking element with a groove extending in a first direction, each male locking element being insertable into the groove of the complementary female locking element in a second direction substantially perpendicular to the first direction with a snapping action which forms a rigid connection irreversible in the second direction but being slidable in the first direction so that the side members can be disassembled by sliding one of the layouts with respect to the other.
Provided also is a method of manufacturing the aforementioned enclosure by extruding the webs of respective layouts simultaneously with their respective locking elements; when it is needed, periodically forming folding means into the web perpendicular to the direction of extrusion; continuously slicing the web into layout-width strips which have locking elements in the proximity of their edges; periodically cutting from the webs the layout-length portions, so that a number of the layouts are produced simultaneously; thereafter assembling the three-dimensional enclosures by folding the complimentary layouts and snapping respective male projections into complementary female grooves.
Rigidity of the enclosure is ensured by the fact that the connection between a male locking element and a complimentary female locking element is irreversible in the direction of insertion. The relative ease of disassembly of the three-dimensional enclosure into its respective layouts is ensured by the fact that the connection between male and complimentary female locking elements can be disconnected by sliding them apart in the direction substantially perpendicular to the direction of insertion.